I'm also experiencing something very similar - my bandwidth is over the monthly limit, and cPanel shows that it's due to IMAP traffic - but I don't use IMAP at all. The only thing that I use / that I have happening is auto-fowarding of emails received by my domain email addresses to a gmail account - but each day these emails total only about 1-4MB per day, whereas the IMAP traffic according to cPanel totals 150-200MB per day! Why????